ADCP-referenced geostrophic velocity and transport in the West Spitsbergen Current

During the summer of 2000 and 2002 (June-July) the West Spitsbergen Current (WSC) was investigated by the Institute of Oceanology, Polish Academy of Sciences. CTD and current measurements by a vessel-mounted Acoustic Doppler Current Profiler (ADCP) were performed along three transects perpendicular to the WSC main stream and covering the region from 76°30' N to 78°20' N and from 02°30' E to 15° E. In general, the geostrophic, baroclinic flow patterns and the ADCP-measured currents were found to be in good agreement but measured current velocities were significantly higher than calculated values. This fact supports earlier observations that the barotropic component is dominant in the WSC. Since ADCP has a better spatial resolution than CTD records, the West Spitsbergen Current could be investigated and described in much greater detail than before. The main stream of Atlantic Water is topographically steered by the continental slope (isobars 800-2000 m) and the complex, multistream structure of the West Spitsbergen Current is clearly visible. The absolutely referenced total geostrophic transport is about three times higher than the estimated value assuming the level of no motion lies at 1000 m

Model-Based Reinforcement Learning for Atari

Model-free reinforcement learning (RL) can be used to learn effective policies for complex tasks, such as Atari games, even from image observations. However, this typically requires very large amounts of interaction -- substantially more, in fact, than a human would need to learn the same games. How can people learn so quickly? Part of the answer may be that people can learn how the game works and predict which actions will lead to desirable outcomes. In this paper, we explore how video prediction models can similarly enable agents to solve Atari games with fewer interactions than model-free methods. We describe Simulated Policy Learning (SimPLe), a complete model-based deep RL algorithm based on video prediction models and present a comparison of several model architectures, including a novel architecture that yields the best results in our setting. Our experiments evaluate SimPLe on a range of Atari games in low data regime of 100k interactions between the agent and the environment, which corresponds to two hours of real-time play. In most games SimPLe outperforms state-of-the-art model-free algorithms, in some games by over an order of magnitude

Numerical modelling of slope–vegetation–atmosphere interaction: an overview

The behaviour of natural and artificial slopes is controlled by their thermo-hydro-mechanical conditions and by soil–vegetation–atmosphere interaction. Porewater pressure changes within a slope related to variable meteorological settings have been shown to be able to induce soil erosion, shrinkage–swelling and cracking, thus leading to an overall decrease of the available soil strength with depth and, ultimately, to a progressive slope collapse. In terms of numerical modelling, the stability analysis of partially saturated slopes is a complex problem and a wide range of approaches from simple limit equilibrium solutions to advanced numerical analyses have been proposed in the literature. The more advanced approaches, although more rigorous, require input data such as the soil water retention curve and the hydraulic conductivity function, which are difficult to obtain in some cases. The quantification of the effects of future climate scenarios represents an additional challenge in forecasting slope–atmosphere interaction processes. This paper presents a review of real and ideal case histories regarding the numerical analysis of natural and artificial slopes subjected to different types of climatic perturbations. The limits and benefits of the different numerical approaches adopted are discussed and some general modelling recommendations are addressed

Current Wildland Fire Patterns and Challenges in Europe : A Synthesis of National Perspectives

Changes in climate, land use, and land management impact the occurrence and severity of wildland fires in many parts of the world. This is particularly evident in Europe, where ongoing changes in land use have strongly modified fire patterns over the last decades. Although satellite data by the European Forest Fire Information System provide large-scale wildland fire statistics across European countries, there is still a crucial need to collect and summarize in-depth local analysis and understanding of the wildland fire condition and associated challenges across Europe. This article aims to provide a general overview of the current wildland fire patterns and challenges as perceived by national representatives, supplemented by national fire statistics (2009-2018) across Europe. For each of the 31 countries included, we present a perspective authored by scientists or practitioners from each respective country, representing a wide range of disciplines and cultural backgrounds. The authors were selected from members of the COST Action "Fire and the Earth System: Science & Society" funded by the European Commission with the aim to share knowledge and improve communication about wildland fire. Where relevant, a brief overview of key studies, particular wildland fire challenges a country is facing, and an overview of notable recent fire events are also presented. Key perceived challenges included (1) the lack of consistent and detailed records for wildland fire events, within and across countries, (2) an increase in wildland fires that pose a risk to properties and human life due to high population densities and sprawl into forested regions, and (3) the view that, irrespective of changes in management, climate change is likely to increase the frequency and impact of wildland fires in the coming decades. Addressing challenge (1) will not only be valuable in advancing national and pan-European wildland fire management strategies, but also in evaluating perceptions (2) and (3) against more robust quantitative evidence.Peer reviewe

Analysis of Core Losses in Transformer Working at Static Var Compensator

This article presents the comparison of 3D and 2D finite element models of a power transformer designed for reactive power compensation stations. There is a lack of studies in the literature on internal electromagnetic phenomena in the active part of a transformer operated in these conditions. The results of numerical 2D and 3D calculations of no-load current and losses in the transformer core were obtained by using various methods and models. The impact of considering the hysteresis loop phenomenon on the calculation of core losses was investigated by using the Jiles–Atherton core losses model. The results obtained in the paper show that the model of the core must contain the areas representing the influence of overlappings on the no-load current and also on the flux density field in the core. The capacitive load of the transformer increases the flux density in the core limbs by several percent, so the power losses there must also increase accordingly. As a summary of the research, differences in the values of losses in each core element between the capacitive load and no-load conditions are presented. The results presented in this paper indicate that considering nonlinearity related to the magnetic hysteresis loop has a significant impact on the calculation of the core losses of power transformers

Ammonium Concentration and Migration in Groundwater in the Vicinity of Waste Management Site Located in the Neighborhood of Protected Areas of Warsaw, Poland

The purpose of the present paper is to assess groundwater contamination by ammonium originating from the waste management site (including composting plant and the landfill) located in the vicinity of protected areas. In this paper, the impact of urban and industrial facilities adjacent to the landfill is also investigated. The analysis of ammonium concentration was carried out for selected piezometers and then the monitoring and laboratory tests results were referred to the Polish standards of groundwater quality. The content of the paper discusses the changes of ammonium concentration in time and space and presents potential reasons for these changes, especially resulting from the construction of the vertical bentonite barrier. The results show the significant decrease of ammonium concentration and progressive improvement of water quality observed in almost every piezometer after a few years since the vertical barrier has been installed. Furthermore, the paper provides statistical analyses of groundwater monitoring data from the period 1998–2015 in order to control the groundwater quality and assess the movement of contamination plume in the landfill area

Comparison of Soil Water Retention Curves for sandy clay, obtained using different laboratory testing methods

The design of engineering structures is still a challenging task when considering unsaturated soil mechanics behaviour. The present paper focuses on analysing Soil Water Retention Curves (SWRC) for clayey soil samples collected from a purpose built experimental embankment. SWRC determination is crucial when analysing geotechnical parameters of the soil. During the measurements, soil samples were subjected to wetting and drying cycles using a stage procedure (where the process is carried out in stages to allow equalisation) and continuous processes. The methods used for obtaining the suction curves were high suction tensiometer, attached at the bottom of the sample, and pressure plates with suctions applied up to 800 kPa. The study compares laboratory methods on measuring suction for sandy clay samples. It proves that the wetting and drying history have an impact on the hydraulic behaviour of tested material. In order to give a wider picture of soil behaviour it also presents the outputs as a function of matric suction and volumetric and gravimetric water content, and degree of saturation

Comparison of Soil Water Retention Curves for sandy clay, obtained using different laboratory testing methods

The design of engineering structures is still a challenging task when considering unsaturated soil mechanics behaviour. The present paper focuses on analysing Soil Water Retention Curves (SWRC) for clayey soil samples collected from a purpose built experimental embankment. SWRC determination is crucial when analysing geotechnical parameters of the soil. During the measurements, soil samples were subjected to wetting and drying cycles using a stage procedure (where the process is carried out in stages to allow equalisation) and continuous processes. The methods used for obtaining the suction curves were high suction tensiometer, attached at the bottom of the sample, and pressure plates with suctions applied up to 800 kPa. The study compares laboratory methods on measuring suction for sandy clay samples. It proves that the wetting and drying history have an impact on the hydraulic behaviour of tested material. In order to give a wider picture of soil behaviour it also presents the outputs as a function of matric suction and volumetric and gravimetric water content, and degree of saturation

Soil water retention curve of silty sand – experimental investigation using different laboratory methods

Most of the infrastructure investments and earthworks not requiring deep foundations are usually designed in the vadose zone to avoid excessive groundwater-structure interactions. The mechanical behaviour of soil material, under partially saturated conditions, is greatly influenced by pore-water tension, known as soil suction, and the characteristics of the Soil Water Retention Curve (SWRC). In the present paper, the SWRC of a silty sand was determined using two different experimental methods. In the first method, a modified pore water pressure transducer was used for suction monitoring, while the specimen was allowed to change its moisture content by natural evaporation. For the second method, a modified consolidation cell fitted with a high air entry value ceramic disc on the base pedestal was used. Suction was applied using the axis translation technique by utilising pore air and pore water pressure controllers, while moisture was monitored using a volumetric measurement system. Through the determination of the SWRC for the silty sand, this paper intends to compare the abovementioned testing methods basedon the produced SWRCs and to reveal advantages and limitations